1. Field of the Invention
The present invention relates to a mobile terminal apparatus, and more particularly to a structure of a mobile terminal apparatus having an upper housing and a lower housing that are connected to each other such that the upper and lower housings are relatively displaceable away from and toward each other to open and close or fold the mobile terminal apparatus.
2. Description of the Related Art
Typically, a mobile terminal apparatus (hereinafter simply referred to as “terminal”) of fold type or clamshell type, such as mobile phone terminal of the type, includes an upper housing, a lower housing, and a hinge portion that connects the upper and lower housings such that the upper and lower housings are turnable about the hinge portion away from and toward each other so that the terminal is openable and closable or foldable. The upper housing has a display screen on an inner major surface thereof, and the lower housing has on an inner major surface thereof an operating portion including various input keys. Fold-type terminals are widely used these days because of their advantages that the screen and key area of the terminals are wide when used, and the terminals are compact when closed to be carried.
When closed or folded, an operating portion of such a fold-type terminal is opposed to a display screen in the form of a transparent plate. A thickness of the terminal becomes inevitably larger when the terminal is folded than when the terminal is not folded, since the upper housing is superposed on the lower housing in the folded state of the terminal. To minimize the thickness of the terminal as folded, it is desirable to minimize a clearance between the upper and lower housings as superposed on each other, in addition to reduce a thickness of each of the upper and lower housings. However, contact of any of the input keys with the display screen leads to contamination or damage of the display screen. When an input key excessively protrudes from the inner major surface, that input key may be unintentionally pressed upon deformation of one or both of the upper and lower housings, thereby causing a false operation of the terminal.
In a common remote controller for a television set or an audio system, input keys or manual operation buttons are disposed in a surface of the remote controller to protrude there from to facilitate operation or pressing thereof by a user.
However, in the fold-type terminal, the keytops of the input keys are substantially flush with the surface in which the input keys are disposed, for the above-described reason. The shape of the keytop of each of the input keys is substantially flat, so as not to form a clearance around each input key. As described above, it is difficult to form the keytop in a rounded shape.
Usually, to alleviate an impact imposed on the upper and lower housings upon folding of the terminal with a clearance left between the upper and lower housings, a shock-absorbing member such as that of rubber is disposed at an end portion of the inner surface of one or both of the upper and lower housings. Increasing a height of the shock-absorbing member allows the input keys to further protrude from the surface in which the input keys are disposed. However, the clearance between the upper and lower housings while the terminal is folded or closed increases with an increase in the amount of the protrusion, or the height, of the input keys, thereby increasing the thickness of the terminal as folded, while making the terminal prone to introduce dust and dirt into the clearance.
JP-A-11-112627 discloses a mechanism in a fold-type mobile terminal having an upper housing and a lower housing, which mechanism is configured such that an operating portion thereof is retracted into the lower housing when the upper and lower housings are turned toward each other, that is, the terminal is folded or closed, and the operating portion comes out of the lower housing when the upper and lower housings are turned away from each other, that is, the terminal is opened.
According to the terminal disclosed in the above-mentioned publication, the usability of the operating portion is enhanced by the mechanism, in exchange for increases in the complexity of the mechanism and the cost of the terminal. Further, although a clearance formed between the upper and lower housings when the terminal is folded can be made relatively small, a space for allowing movement of input keys a direction of a thickness of the lower housing is necessary in the lower housing, and thus it is inevitable that the thickness of the lower housing is relatively large.